Please help me to bring a 3-5 AES back to life (no sound, no picture)

[Boomchild]

Hi everyone.

I've just bought an AES 3-5 which is in good looking state, but refuse to work. The seller said that it hasn't been used for a long time.

Here are the symptoms :

- No sound, even in the headphone jack
- No video, BUT my CRT TV switch to AV when I power on the console. However all I get is a black screen using RGB cable.
- My OSSC doesn't get any sync signal

Here are the different checks I've already made :

- The board seems to be fully powered, I get 5V where it should be.
- The board haven't been messed with. No RGB bypass, no Unibios.
- The power adapter and video cable work fine with my 3-6 AES
- The video connector is OK, I've checked the connection between the solder joints underside to the scart pins
- The traces from the BIOS, 68k, Work RAM et Video RAM are all OK. I've checked visually for broken traces but haven't found any.


Some suspicious things I've seen :

On the other side of the BIOS, there are small "bubbles" (?). They are only located there, and don't seem to mess with the traces.


Underneath the Neo-G0, the white outline is brown. It may just be dirt but that's strange :



I just have a multimeter but can get access to an oscilloscope at work, if there are some checks to be made.

Thanks everyone in advance for your help, hopefully we can bring it back from the dead !

 

[Neo Alec]

Have you confirmed it's the correct AC adapter for the console? (5v system or not?)

What cartridge are you using to test?

Do you have a cable to test with plain old composite or RF?

 

[Boomchild]

It’s a 9V 1A adapter that works fine with my 3-6 AES. I’ve also tested with a Megadrive 1 adapter, with the same results.

I’ve tried with the original composite cable, and all I get is flashing white lines on black background.

I ran my tests without a cartridge but I also tested with a Samurai Spirit that works with my 3-6, it doesn’t change anything.

PS : Are you the Neo Alec from Basement Brothers ? I LOVE your Neo Geo Generation videos, they are by far among the best I’ve seen, congratulations !

 

[Neo Alec]

What does it say on the bottom of the 3-5 system you're troubleshooting? Also, can you post a pic of the complete motherboard (top side)?

Thanks for your compliments on my Youtube series. Glad you've been watching.

 

[Boomchild]

Here is the pic :


The label on the bottom is damaged but it seems to say "Use PRO-POW-E"

I should mention that I've checked the LM and the voltage is good. Also, the red led lights up when I power on the console.

Edit : I've put an Unibios on it (piggybacked) and it hasn't change anything. So the BIOS is not the culprit here.

 

[Neo Alec]

Thanks. Power etc look good at first glance.

If you've socketed the bios, you'd might as well try the Diag bios now and see what it says:

GitHub - jwestfall69/neogeo-diag-bios: Disassembly of smkdan's Neo Geo Diagnostics BIOS with added features

Disassembly of smkdan's Neo Geo Diagnostics BIOS with added features - jwestfall69/neogeo-diag-bios

github.com

 

[Boomchild]

I have one already. Will it be of any help if I can’t get any video signal ?

 

[maki]

-- oops - misread the first post

 

[venchia3]

The “white bubbles” underneath the board where the bios is located look to me as a result of use of an hot air gun.

It may happen at times that using it to complete the desoldering of an IC gives that result if temperature is set slightly too high or hot air hit the board for too long

 

[Neo Alec]

I have one already. Will it be of any help if I can’t get any video signal ?

Well, since we don't know why you're not getting a video signal, I guess the hope is that the video itself isn't the issue, and that you might get a signal with the Biag bios.

I'm afraid @venchia3 probably has a point though, now that he mentions it. Have you checked the traces around the bios for continuity?

Bios Pinout for 1st Gen AES

I have a customers AES that needs repair and it's currently stuck in watchdog. The only pinout I have is from a 3-4, the 1st gen doesn't have a Neo-E0 chip so I need to know a complete pinout for the 1st gen.

www.neo-geo.com

 

[Boomchild]

Yes I've checked all the traces from the BIOS, 68K, VRAM and Work RAM with a multimeter, all are OK.

I'll try with the diagnostic bios and report back.

 

[maki]

- No sound, even in the headphone jack
- No video, BUT my CRT TV switch to AV when I power on the console. However all I get is a black screen using RGB cable.
- My OSSC doesn't get any sync signal

The CRT switching is probably due to the switching voltage being present, it is expected since you've verified the voltages.
So no sync at all at the OSSC, not even a fast changing one?

I agree that it looks reworked from the pics, the white spots are delamination caused by excessive heat, at that area I'd also expect a hot air station to be involved.
The G0 you're showing looks reflowed (looks like very shiny solder joints), the brown goo underneath looks like flux form that reflow.
Yes it would be odd to replace a stock BIOS with a stock BIOS, but weirder things have happened..

Even badly damaged MVS would at least have a boot loop if the 68k worked somewhat IMO, so I'd try to check that one and the NEO-D0, you have an oscilloscope or logic probe?
Check pin 15 for the 68k clock: https://wiki.neogeodev.org/index.php?title=68k
also check the others clocks on the NEO-D0 (it functions as clock divider): https://wiki.neogeodev.org/index.php?title=NEO-D0

 

[Boomchild]

Thank you for your answers and sorry for the delay, I didn't have access to an oscilloscope until today at work.

I've brought my working 3-6 and dead 3-5 and made some tests, and it seems the problem is coming from the LSPC2-A2 (sigh), it doesn't output the 8Mhz frequency on pin 148 whereas my 3-6 does.

I've got one spare one on a MVS board with sound problems, so I'll take it. Is there anything I should know before attempting the replacement ? I've got an hot air station but I'm somewhat afraid to mess up.